Isothermal and Cyclic Oxidation Behavior of Fe–B Based Alloys at 927 K

Abstract

The microstructure and oxidation kinetics of Fe–B-based alloys at 927 K in air with different boron concentrations of 0.95, 1.45, 2.10, and 3.08 wt% were studied. The alloy microstructures were interpreted to consist of α-Fe, Fe2B, and pearlite. After 100-h oxidation, the oxides comprised Fe2O3 at the surfaces and a mixed B2O3–SiO2 layer at matrix/oxide interface. The formation of mixed oxides layer was affected by boron content in the alloy and had obvious influence on the oxide morphology. The isothermal oxidation kinetics at 973 K exhibited initial rapid mass loss followed by slow mass loss, and the oxidation rate constants of the two oxidation stages demonstrated completely opposite tendencies with the increase of boron. The Fe–B 3.08 wt% alloy exhibited the best oxidation resistance after 100 h of cyclic oxidation due to the formation of a well-distributed and continuous B2O3–SiO2 mixed oxide layer.